ANDROID: remove .patch, patches from .gitignore

The Android-specific modifications to kselftest are tracked by a
directory of patches at android/patches. Remove the required entries
from .gitignore so these files are visible in git.

Change-Id: I7a359da279ab90b5ae5426e720230021dea395bd
Signed-off-by: Steve Muckle <smuckle@google.com>